1. Field of The Invention
The present invention relates to control systems for remote onshore and offshore, subsea wellheads and more particularly relates to an improved electric or electro-hydraulic control system for wellheads especially subsea wellheads wherein an audible "touch tone" type operation allows remote opening and closing of the wellhead valving members as the tones are "interpreted" at the wellhead so that an electric motor is activated to operate a valve or blowout preventor. The system is also useful for operation of remote valves on a pipeline which are located in a remote location.
2. General Background
There are many offshore oil well wellheads which are remote and or under the water surface or in a subsea environment. These wellheads typically are equipment with numerous valves or blowout preventors for controlling fluid flow through the wellhead assembly which is typically in the form of a tree or Christmas tree or blowout preventor stack as is known in the art. The operation of these valves from a remote location would be desirable because of the time and expense connected with operating these subsea valves or blowout preventors manually using divers or by dispatching workers. Similarly, many pipelines have remote valves which would be desired to operate without divers or workers.